by A new investigation into a rare and short-lived type of galaxy has revealed that such objects harbor supermassive black holes that wake up briefly to rip apart a massive star and eat its remains like a giant cosmic breakfast.
“Symmetric Compact Objects,” or CSOs, are active galaxies that have two jets blasting out from them at nearly the speed of light. These jets are common to active galactic nuclei (AGN), which have supermassive black holes that feed the surrounding gas and dust into their cores – but the jets of CSOs are different.
While jets from AGNs can stretch for 230,000 light-years in both directions, the jets of the CSO are stunted, stretching for 1,500 light-years or so.
Scientists have previously theorized that CSO jets are short because they are fledgling or young. Now, a team led by California Institute of Technology (Caltech) scientists has determined that these jets only have a short lifespan.
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“These CSOs are not young. You wouldn’t call a 12-year-old dog young even though it has a shorter lifespan than an adult,” study team leader Anthony Readhead, professor emeritus of astronomy at Caltech, said in a statement . “All these objects are a distinct species that live and die over thousands of years, rather than the millions of years that are common in galaxies with large jets.”
Black hole snacks give galaxies the life of a dog
To solve the mystery of the CSOs and reveal their true nature, Readhead and his colleagues spent two years sifting through 3,000 CSO candidates in past literature and astronomical data from the Very Long Baseline Array (VLBA). and other high-resolution radio telescopes.
“The VLBA observations are the most detailed in astronomy, providing images with detail equivalent to measuring the width of a human hair across 100 miles [160 kilometers],” Readhead said.
The team confirmed 64 of these candidates as CSOs and also spotted 15 of those rare galaxies. Analyzing these CSOs, the team concluded that these rare types of galaxies emit jets every 5,000 years or less and then disappear.
“CSO jets are very energetic jets, but they seem to stall,” said team member Vikram Ravi, an assistant professor at Caltech. msgstr “The jets stop flowing from the source.”
The team has identified a suspect in the emission of these jets: they theorize that supermassive black holes at the core of CSOs are tearing apart stars that pass too close in “tidal disruption events.” or TDEs.
When stars venture too close to a black hole, the latter’s mass of gravity generates powerful tidal forces within the galactic body. These tidal forces stretch the star vertically while squashing it horizontally, a process known as “spaghetization.”
This noodle wraps around a star, creating a disk of material that is gradually consumed by the supermassive black hole. But black holes are restless people, and some of this cosmic matter is sent to the poles of these cosmic monsters. From there, some of the material is blasted out as jets. This TDE process is accompanied by extremely bright light emissions that advertise these supermassive black holes to astronomers.
“We think that one star is torn apart, and then all the energy is distributed in jets along the axis the black hole is spinning around,” explained Readhead. “The huge black hole starts out invisible to us, and then when it consumes a star, boom! The black hole is fuel, and we can see it.”
It is not only, however, that it is just any star that could be the cosmic messy meal that wakes up a black hole as CSO. The team believes that CSOs are only created when a massive star is destroyed by a supermassive black hole in TDE.
“The TDEs we’ve seen before only lasted a few years,” Ravi explained. “We think that the significant TDEs powered by CSOs last much longer because the disturbed stars are very large, very massive, or both.”
Readhead and colleagues were also able to create a “cosmic family album” showing how CSOs and their jets change over time. Younger CSOs that are closer to the central supermassive black hole have shorter jets, while older CSOs have longer jets that extend further from the location of the TDE.
The team determined that while the vast majority of CSOs will die, 1% will have long-term events with extended jets like those seen in Cygnus A, a distant supermassive black hole whose jets are directed towards the Earth, a class of objects called blazar.
In those 1-in-100 long-lived events, the researchers suggest that the central black hole is feeding additional gas and dust through the merger of its host galaxy with another.
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For Readhead, these results reflect a theory he first stated in the 1990s, when only three Central Statistics Offices were found. This idea was not recognized by the wider scientific community when it was first proposed but should gain traction with this new evidence.
“The hypothesis was not abandoned because of the years that passed before observational evidence began to mount for TDEs,” Readhead said. “These objects are indeed a distinct population with their own distinct origins, and it’s now up to us to learn more about them and how they came to be.
“If these things can be studied on time scales of decades to decades rather than millions of years it opens the door to a whole new laboratory for studying supermassive black holes and the many unexpected and impossible surprises predict.”
The team’s research was published last month across three studies in The Astrophysical Journal.
